Electron gun evaporation apparatuses are extensively used in various fields of industries as apparatuses for forming films on the surfaces of objects. Especially in the manufacture of various electronic parts such as a magnetic head and magnetic disk, electron gun evaporation apparatuses are often used to form various conductive films and insulating films.
An outline of the arrangement of a conventional electron gun evaporation apparatus will be explained below with reference to FIG. 4.
An electron gun 6 comprising an electron beam generator 61, electron gun scanning coil 62, and crucible 63 is placed in the lower portion of a vacuum chamber 1 that can be evacuated. The apparatus also includes a film thickness controller 13 for detecting and controlling the film thickness growth rate of a film formed on a substrate 3 placed in the vacuum chamber 1. The apparatus further comprises an electron gun power supply 10 for supplying a high voltage to the electron beam generator 61, a filament controller 11 for controlling the filament power of the electron beam generator 61, a sweep controller (SWEEP controller) 12 for controlling the position of an electron beam that impinges on an evaporation source 7 in the crucible by supplying a direct current to the electron gun scanning coil 62, and an apparatus controller 14 for controlling the electron gun apparatus.
The filament controller 11 installed outside the vacuum chamber 1 supplies electric power to the filament of the electron beam generator 61, thereby turning on the filament. The filament controller 11 supplies a high negative DC voltage (−6 to −10 kV) to the electron beam generator 61 to generate an electron beam.
An evacuating means 2 evacuates the vacuum chamber 1 to a vacuum degree of 1.0E-4 to 1.0E-6 Pa. A substrate holder 4 on which the substrate 3 is placed is installed in the upper portion of the vacuum chamber 1, and a film thickness sensor 5 for monitoring the film thickness is installed below the substrate holder 4. The film thickness controller 13 is connected to the film thickness sensor 5. The film thickness controller 13 can detect the film thickness growth rate of a film formed on the substrate 3 on the basis of that film thickness of the film formed on the substrate 3 which is measured by the film thickness sensor 5.
The electron beam generator 61 of the electron gun 6 generates an electron beam by receiving the high negative DC voltage (−6 to −10 kV) supplied from the electron gun power supply 10. The electron gun scanning coil 62 deflects the electron beam generated by the electron beam generator 61 through about 180°, and controls the electron beam irradiation position. The crucible 63 is a receiver for the evaporation source 7 for film formation. The crucible 63 itself is cooled by a cooling mechanism.
The process of forming a film on the substrate 3 placed on the substrate holder 4 by using the conventional electron gun evaporation apparatus having the above arrangement will be explained below.
While the interior of the vacuum chamber 1 is at the atmospheric pressure, the substrate 3 is placed on the substrate holder 4, and the evaporation source 7 is supplied to the crucible 63. When these preparations are completed, the vacuum chamber 1 is closed, and the evacuating means 2 evacuates the vacuum chamber 1 (until the vacuum degree reaches 1.0E-4 Pa). When this evacuation is completed, cooling water is supplied to the cooling mechanism for cooling the crucible 63, and the electron gun power supply 10 is operated to apply a set negative DC voltage. The applied voltage is −6 to −10 kV.
When the high voltage is completely set, a predetermined emission current value is set by monitoring an emission current meter. The value of the emission current increases in proportion to the electric power applied to the filament. When the emission current flows, the electron beam generator 61 applies an electron beam to the evaporation source 7 in the crucible 63, and this electron beam heats the evaporation source 7. The electric power of this electron beam is the product of the applied voltage and emission current of the electron beam generator 61.
Generally, if the electron gun applied voltage is 6 kV and the emission current is 1 A when evaporating an Al material, the electron beam power is 6 kW. When the electron beam impinges on the evaporation source 7 after that, the evaporation source 7 is heated to a high temperature and starts evaporating, and an evaporated film adheres to the substrate 3 placed on the substrate holder 4. When a predetermined film thickness has adhered to the substrate 3, the power supply to the filament is stopped, so the emission current becomes zero.
When the emission current becomes zero, the power of the electron beam also becomes zero, so the application of the electron beam to the evaporation source 7 stops.
The film thickness sensor 5 measures the film thickness on the substrate 3. On the basis of the measurement result from the film thickness sensor 5, the film thickness controller 13 connected to the film thickness sensor 5 calculates the film thickness growth rate during film formation, and calculates a film formation time required to obtain a predetermined film thickness by using the following equation, thereby managing the film formation time. By thus managing the film formation time, the film thickness controller 13 controls film formation for forming the predetermined film thickness on the substrate 3.(Film thickness of substrate 3)/(film thickness growth rate)=film formation time
When the film having the predetermined film thickness is completely formed, the application of the voltage is stopped by stopping the electron gun power supply 10, thereby completing the film formation process.
In some conventional electron gun evaporation apparatuses, however, the evaporation source supplied into the crucible does not uniformly and evenly reduce because the electron beam spot of the electron gun, that is, the irradiation position of the electron beam is fixed.
To make the reduction of the evaporation source uniform and even, therefore, a method of averagely evaporating the evaporation source by scanning the electron beam irradiation position in the X- and Y-axis directions has been proposed (patent reference 1).    Patent reference 1: Japanese Patent Laid-Open No. 11-200018